Electrostatic charging process for electrophotographic photosensitive material

ABSTRACT

An electrostatic charging process for electrophotographic photosensitive material which comprises irradiating uniformly a photoconductive insulating layer provided on a translucent support material from the back side thereof with light absorbable by the photoconductive insulating layer thereby rendering the back surface of the photoconductive insulating layer electroconductive, simultaneously irradiating the edge portion of the photoconductive insulating layer with light absorbable by the photoconductive layer thereby forming on the edge portion an electroconductive area substantially connected with the electroconductive area formed on the back side of the photoconductive insulating layer, and applying corona discharge onto the photoconductive insulating layer keeping a grounded conductor in contact with the edge portion while the electroconductivity persists thereby supplying electrostatic charge onto the layer.

United States Patent 1 1 Sato et al.

11] 3,749,927 1451 July 31,1973

[ ELECTROSTATIC CHARGING PROCESS FOR ELECTROPIIOTOGRAPHIC PHOTOSENSITIVE MATERIAL [75] Inventors: Masamichi Sato; Seiji Matsumoto;

Osamu Fukushima; Satoru Honjo, all of Asaka, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan 22 ,Filed: July 2,1971

[211 Appl. No.: 159,363

[30] Foreign Application Priority Data July 3, 1970 Japan 45/58607 [52] US. Cl. 250/49.5 ZC, 96/1, 96/15, 355/3, 355/16 [51] Int. Cl..... G03g 5/00, G03g 15/00, l'IOlj 37/26 [58] Field of Search 96/1, 1.5; 355/3, 355/16; 250/495 ZC [56] i References Cited UNITED STATES PATENTS ll/l966 Weigl et a] .L 96/1 R l/l97l Hodges 96/].5

3,533,692 iO/l970 Blanchette et al 355/i6 Primary Examiner-James W. Lawrence Assistant,Examiner-T. N. Grigsby Attorney-Gerald J Ferguson, Jr.

[57] ABSTRACT An electrostatic charging process for electrophotographic photosensitive material which comprises irradiating uniformly a photoconductive insulating layer proconnected with theelectroconductive area formed on the back side of the photoconductive insulating layer, and applying corona discharge onto the photoconductive insulating layer keeping a grounded conductor in contact with the edge portion while the electroconductivity persists thereby supplying electrostatic charge onto the layer. A

a 5 Claims, 8 Drawing Figures T T lfl PATENTED JULB l 3 SHEEI 1 0f 2 FIG. I

II I 1 Ill/l 1/. 1 11 IIIIl/II III/III II/Ij/I III/ I FIG.4

INVENTORS. MASAMICHI SATQ SEIJI MATSUMOTO OSAMU FUKUSHIMA SATORU HONJO BY W ATTORNEYS.

PATENIEU JUL 3 1 I973 SHEET 2 OF 2 FIG. 5

FIG. 7

FIG. 8

'INVENTORS, MASAMICHI SATO SEIJI MATSUMOTO 82% FUlUSHIMA u H NJO BY 4 M 25. ATTORNEYS.

1 ELECTROSTATIC CHARGING PROCESS FOR ELECTROPI-IOTOGRAPHIC PI-IOTOSENSITIVE MATERIAL DETAILED DESCRIPTION OF INVENTION This invention relates to an electrostatic charging process adapted for electrostatically charging a photoconductive insulating layer on a support material for electrophotographic photosensitive material.

Conventional electrophotographic photosensitive material generally consists of photoconductive insulating layer provided on an electroconductive support material such as metal plate, or of an insulating photoconductive layer provided on an electroconductive undercoating layer composed for example of evaporated metal layer or electroconductive resin which in turn is provided on an electroinsulating support material such as paper or plastic film. Electrostatic charging of the photosensitive material of the former structure is carried out by grounding said electroconductive support material and applying corona discharge onto said photoconductive layer thereby supplying-corona ions to said layer, while that for the latter structure is realized in a similar manner by grounding said electroconductive undercoating layer and supplying corona ions to said photoconductive layer.

In the case of latter structure, however, it is difficult to ground said electroconductive undercoating layer if said layer is composed of thin metal evaporated film or is provided with relatively high resistance (volume specific resistance of 10 ohm. cm). In prior processes, in order to ground the electroconductive layer of said kind sandwiched between the support material and photoconductive layer, the photoconductive layer is provided so as not to cover the whole areaof said electroconductive subcoating layer toexpose said subcoating layer in the peripheral portion which is utilized for connection or contact with grounded conductor. The preparation, however, of photosensitive element with such locally exposed electroconductive layer requires complicated manufacturing procedure. Also electroconductive layer consisting of evaporated metal film shows insufficient mechanical strength and often loses the electroconductivity thereof due to scratches during the use.

This invention is to provide an electrostatic charging process suitable for use with the photoconductive material layer of this kind provided on an insulating support material. Furthermore this invention is to provide a process capable of charging photoconductive insulating layer directly provided on an insulating support material without providing an electroconductive layer directly behind said layer as in the case of two photosensitive elements explained above.

In British Pat. 971,281 disclosed is an electrostatic charging pro'cessfor a photosensitive material similar to that to be employed in the process of this invention. Said process consists of irradiating uniformly the photoconductive layer from the back side thereof with light absorbable by said layer thereby rendering said layer electroconductive temporarily and applying electrostatic charge in this state onto the surface of said photoconductive layer by meansfor example of corona discharge. This process, though practicable when the thickness of insulating support material is sufficiently small and the electroconductivity of back side of photoconductive layer becomes relatively large by means of uniform irradiation of light from the back side trostatic charging process for electrophotographic photosensitive material which comprises irradiating uniformly a photoconductive insulating layer provided on a translucent support material from the back side thereof with light absorbable by said photoconductive insulating layer thereby rendering the back surface of said photoconductive insulating layer electroconductive, simultaneously irradiating the edge portion of said photoconductive insulating layer with light absorbable by said photoconductive area substantially connected with the electroconductive area formed on the back side of said photoconductive insulating layer and applying corona discharge onto said insulating photoconductive layer keeping a grounded conductor in contact with said edge portion while said electroconductivity persists thereby supplying electrostatic charge.

The process of this invention will be further clarified in the following with reference to the ings. I

BRIEF EXPLANATION OF THE DRAWINGS FIG. I shows the enlarged cross section of an example of electrophotographic material to be employed in the process of this invention.

FIG. 2 is the elevational view of an example of device for effecting the process according to this invention.

FIG. 3 is a cross-sectional side view of said device in the central portion thereof.

FIG. 4 is the cross-sectional elevational view of the device shown in FIG. 2 in the central portion thereof.

FIGS. 5-7 are the drawings showing the basic principle of the process according to this invention.

FIG. 8 is the cross-sectional elevational view of an other example of the device for effecting the process according to this invention.

In FIG. 1 showing a cross-sectional view of an example of electrophotographic material to be employed in the process of this invention represented are said elecattached drawtrophotographic photosensitive material 10 composed of a photoconductive insulating layer 11 and a translucent insulating support material 12. Said layer ll can be composed of various photoconductive materials such as blended composition of photoconductive zinc oxide powder and insulating resin, organic photoconductive material, amorphous selenium etc. Also said supportmaterial 12 can be composed for'example of plastic film or plate such as polyester, polyethylene, polypropylene, polyvinyl chloride, polyvinyldene chloride, polycarbonate or triacetyl cellulose, or glass plate. Plate herein shall mean a thickness of several millimeters to several tens millimeters or even larger.

In FIG. 2 showing an example of device adapted for use in the process of this invention represented are a corona discharge device 20, an irradiating device for edge portion 21, an irradiating device for back side 25, and pinch rollers 22 and 24 for holding and advancing said electrophotographic photosensitive material 10.

Said roller 22 is provided with electroconductive 1 flanges 23 with slightly larger diameter which ground the back surface of insulating photoconductive layer in contact with the edge surface of said electrophotographic photosensitive material 10.

In FIG. 3 showing the longitudinal cross-section in the central part of the device shown in FIG. 2 represented are a corona discharge device 20 composed of a corona discharge wire 30 and a shield case 31, and the irradiating device'25 for back side composed of a lamp 32 and a lamp case 33.

In FIG. 4 showing the cross-sectional elevation in the central portion of the device shown in FIG. 2 represented is a corona discharge wire 30 mounted on an insulator 43 fixed to said shield case 31. The irradiating device 21 for the edge portion is composed of a lamp 40 and a lamp case 41, and said lamp 40 is mounted on a socket (not represented) fixed on said case 4. The light of said lamp 40 is directed, through an opening 42 provided on the lower end of said case 41, to the edge portion of said electrophotographic photosensitive material 10. The irradiating device 25 for the back side is composed a lamp 32 and a lamp case 33, and said lamp 32 is preferred to be shaped ofa long tube covering the width of the back side of electrophotographic photosensitive material 10. The lamp 32- is supported by a socket (not represented) fixed on said case 33. The lamp 32 can be composed for example of fluorescent lamp, mercury lamp, tungsten lamp, etc., whereas the lamp 40 is composed for example of tungsten lamp or mercury lamp. The light of said lamp 40 is preferred to be absorbed over the whole thickness of said photoconductive layer 11, whereas the light of said lamp 32 is preferred not to be absorbed by the whole thickness but by the back surface of the vicinity thereof of said photoconductive layer. For example in case that the photoconductive layer is provided with sensitivity over the visible and ultraviolet wavelength range with stronger absorbability for ultraviolet light, it is desirable to emit ultraviolet light and visible light from the lamp 32 and lamp 40, respectively.

FIG. 5 shows the basic principle of the example of this invention. As shown in this drawing, the photoconductive layer is wholly exposed from the back side thereof to the irradiation of ultraviolet light, the major portion of which is absorbed at the vicinity of the back surface of said photoconductive layer to form an electroconductive portion 50 at the back surface of said photoconductive layer 11. At the same time the edge portion of said photoconductive layer 11 is exposed to the irradiation of visible light, whihc is absorbed over the whole thickness ofsaid photoconductive layer 11 to form an electroconductive area 51. Thus the electroconductive'areas 50 and 51 are satisfactorily connected electrically each other, and said electroconductive area 51 is therefore securely grounded by contacting a grounded conductor such as the flanges 23 of the roller 22 shown in FIG. 2 with said area 51. Thus, as readily observable from FIG. 5, the process of this invention is capable of electrostatically charging the insulating photoconductive layer 11 provided on the insulating support material 12 irrespective of the thickness of the support material l2.

FIG. 6 shows the basic principle of another example of the process according to this invention in which the visible light irradiation for the edge, portion in FIG. 5 is replaced by ultraviolet light. Since ultraviolet light is almost absorbed in the vicinity of the surface of photoconductive layer 11 to form a surfacial electroconductive area 60 instead of forming electroconductive area over the whole thickness of said photoconductive layer 11. Nevertheless it is possible to ground said area 50 practically by contacting a grounded conductor with said area 60 as the distance between said areas 50 and 60 is extremely small.

FIG. 7 shows the basic principle of further another example of the process according to this invention in which ultraviolet irradiation on the edge portion is made in slanted direction with respect to the surface of photoconductive layer instead of approximately vertical irradiation in case of FIG. 6 so as to irradiate simultaneously the cross-sectional portions thereof with ultraviolet light. Thus, in this example, the electroconductive areas 50, and 71 are formed continuously from the back side 6 through the cross sectional portion to the edge portion of surface of photoconductive layer 11.

FIG. 8 shows the schematic structure of the device adapted for use in the example shown in FIG. 7, in which the case of the lamp 32 is provided with wing portions 81 to cover also the edge portion of the electrophotographic photosensitive material 10. The internal surface of said case 80 reflects the light of the lamp 32 to irradiate the edge portion of electrophotographic photosensitive material 10 vertically and slantedly as shown in FIG. 7 thereby forming connected electroconductive areas 50, 70 and 71 as shown in FIG. 7. Although it is explained in the above example that the irradiation on the edge portion, that on the back surface and electrostatic charging by corona discharge are car-' ried out simultaneously, it is also possible to effect the irradiation on the whole back surface, that on the frontal edge portion and corona discharge'in this order. More specifically two irradiations to form electroconductive areas can be carried out in an arbitrary order so long as the electrostatic charging by corona discharge is carried out thereafter.

As thus far explained this invention enables to provide a mechanically stable grounding terminal with substantially satisfactory electroconductivity for corona discharge in the edge portion of surface of electroconductive layer by an extremely simple means thereby realizing electrostatic charging assuredly irrespective of the thickness of the translucent support material for the photoconductive insulating layer or the electroconductivity of said support'material.

Another advantage of this invention lies in' the fact that this process enables the use of substantially insulating support materials with high electric resistance in addition to low resistance support materials such as potassium polyvinylbenzene sulfonate, polyvinylbenzyl trimethyl ammonium chloride, etc. Such polar poly mers often show insufficient adhesion to the photoconductive layer particularly to organic photoconductive layers, but the process of this invention enable satisfactorily the use of high resistance support materials with improved adhesion such as polyvinyl alcohol, sodium polyacrylate, sodium polymethacrylate, maleic acidvinyl acetate copolymer, maleic acid-vinylmethyl ether copolymer, etc.

What is claimed is:

1. An electrostatic charging process for electrophotographic photosensitive material which comprises i rradiating uniformly a photoconductive insulating layer provided on a translucent support material from the back side thereof with light absorbable by said photoconductive insulating layer thereby rendering the back surface of said photoconductive insulating layer electroconductive, simultaneously irradiating the edge portion of said photoconductive insulating layer with light absorbable by said photoconductive layer thereby forming on said edge portion an electroconductive area substantially connected with the electroconductive area formed on the back side of said photoconductive insulating layer, and applying corona discharge onto said photoconductive insulating layer keeping a grounded conductor in contact with said edge portion while said electroconductivity persists thereby supplying electrostatic charge onto said layer; 7

2. A charging apparatus for electrophotographic material which comprises a device for holding and advancing an electrophotographic material consisting of a transparent insulating support and a photoconductive insulating layer provided thereon, a corona discharge device facing said photoconductive layer of electrophotographic material, a light source facing said support of electrophotographic material, a lighting means for the lighting edge portion of said photoconductive layer, and an earth terminal contacting said lighted edge portion of said photoconductive layer.

3. A charging apparatus as claimed in claim 2, wherein said lighting means for the lighting edge portion of the photoconductive material comprises a light source and a case enclosing said light source with a slit opening to said edge portion.

4. A charging apparatus as claimed in claim 2, wherein said lighting means for lighting the edge portion of the photoconductive material comprises a re- .flector which reflects the light of said light source facing to the support of electrophotographic material towards said edge portion.

5. A charging apparatus as claimed in claim 2, wherein said earth terminal is at least one of a plurality of electroconductive rollers in contact with said electrophotographic material for holding and advacing said electrophotographic material. 

2. A charging apparatus for electrophotographic material which comprises a device for holding and advancing an electrophotographic material consisting of a transparent insulating support and a photoconductive insulating layer provided thereon, a corona discharge device facing said photoconductive layer of electrophotographic material, a light source facing said support of electrophotographic material, a lighting means for the lighting edge portion of said photoconductive layer, and an earth terminal contacting said lighted edge portion of said photoconductive layer.
 3. A charging apparatus as claimed in claim 2, wherein said lighting means for the lighting edge portion of the photoconductive material comprises a light source and a case enclosing said light source with a slit opening to said edge portion.
 4. A charging apparatus as claimed in claim 2, wherein said lighting means for lighting the edge portion of the photoconductive material comprises a reflector which reflects the light of said light source facing to the support of electrophotographic material towards said edge portion.
 5. A charging apparatus as claimed in claim 2, wherein said earth terminal is at least one of a plurality of electroconductive rollers in contact with said electrophotographic material for holding and advacing said electrophotographic material. 